Not sure where the moderator gets the weather information for Cairns and Far North Queensland from but I can assure you the weather is fine...no rain for weeks...the visibility on the reef was 18 m last week but this varies on a daily basis depending on the wind.
The original question was about the five weeks starting on the 2nd of January, not about right now, and then I get my information from the climate charts in my lonely planet, which show really high bars (over 400mm) for Cairns for the months of January and February.
ah well, it still helped to know what it's like at the moment. i'm thinking of travelling from Cairns down to Sydney in august for a month...hoping that's a good time and a little cheaper too...
Just following on from the question re: diving up north, we go up to Pt Douglas (just north of Cairns) in March every year for our wedding anniversary which is definite wet season and stinger season but we always have an amazing time! Every time we have seen some gorgeous fish, coral and turtles. We normally go for 4-7 nights and we always have at least 2-3 calm and sunny days.
I have been to Cairns in high season and it is so much more crowded, so you do get the benefit of less people in the wet season too.
DO NOT miss the reef, it is an awesome experience!
I have been to north Queensland during summer and snorkelled on the reef and it was brilliant!! Of course, everyone is right, it will be ridiculously hot and humid, but its north queensland, it's always hot and humid!!
As for the stingers, obviously you will be going in peak season, but all tours out on the reef will provide you with a "stinger suit". It’s a full body lycra suit with long sleeves, covers all your legs, and comes right up to your neck, so it will protect you from any nasties. And besides, I know someone who has been stung by an irukandji and he is fine. A few days in hospital and he was back out on the reef! what a trooper!
As for the visibility, it was absolutely perfect when I went. I was under the impression that if visibility in the water was going to be too low they would cancel the tour, or postpone it to another day.....
I would recommend going to cairns and travelling down from there. There is more rain in february than in January i think.
Anyway, hope you enjoy your trip!!
As a friend who was in cairns a few years ago for new year said to me, its not worth letting the weather stopping you going between cairns and brisbane theres so many amazing places to go up north